This was a knife custom designed to be an optimal low stress cutting tool. D2 was a standard use by Mel Sorg for this type of blade, it has excellent characteristics for such use having a very high wear resistance and obtainable hardness of 62 HRC. The stock thickness was 3/32", just enough to make the blade rigid. The knife had a four inch blade, and the D2 uniformly heat treated to 62 RC, including a full liquid nitrogen cryogenic heat treatment. The scales were Kingwood, formed in a durable and comfortable grip. The blade had a fine drop point for controlled detailed work and a slight recurve to enhance slicing ability. The sheath is a simple design, thick leather with a fold over belt loop. The total cost was only $130.
UPDATE : Mel Sorg passed away shortly after this knife was made. The Mel Sorg's website, is still up in memory and there is also A Tribute to the Madpoet website as well.
The knife came with a high polished convex edge. The stock, while thin, but still very stiff due to the high hardness, it does not flex enough to be noticeable during even heavy cutting. The knife cuts very well due to the thin stock and narrow and acute edge. The custom easily vastly outcuts a mini-AFCK in M2, which was reground significantly thinner than the Benchmade standard edge. Commparing the two over a few days of cutting cardboard, rope, hard plastics, some soft metal (thin aluminium), the mini-AFCK degraded significantly while the D2 blade was not significantly effected. The handle is very ergonomic, confortable in a variety of grips, and secure enough even when wet to handle most cutting tasks.
This custom was used as a reference against many other blades. With the combination of high hardness and wear resistance, plus very efficient edge geometry, this custom from Mel Sorg sets a very high reference for cutting ability and edge retention. Some specifics :
Other details can be seen in some other reviews [ref].
The second method is to use an abrasive which has some give and thus the curvature is matched automatically. The edges are often formed initially with use of a slack belt sander, and that also works well for sharpening - but is a little overkill. Thick leather can also be used when charged with a honing compound. A stropping motion (edge trailing) is used for such honing. Sandpaper on top of styrofoam (or anything similar) can also be used. High quality sandpaper will be need, that which is designed to polish metals.
The knife was used to cut 3/8" hemp with a two inch draw with the force required to make a cut measured on a scale. The sharpness was also tested periodically by push cutting light thread and slicing 1/4" poly under 1000 grams of tension. The initial edge geometry was basically kept as initially, with slight thickening and removal of the recurve from repeated sharpenings. The final edge applied was set at a 22 degree micro bevel with a fine ceramic rod. The results :
|# hemp cuts||Thread||Poly||Hemp|
|0||125 +/- 24||0.50 +/- 0.06|
|2||175 +/- 24||0.75 +/- 0.08||28.0 +/- 1.3|
|6||185 +/- 33||0.95 +/- 0.15||30.0 +/- 3.9|
|14||235 +/- 31||1.60 +/- 0.10||33.0 +/- 1.3|
|30||250 +/- 20||2.20 +/- 0.31||31.0 +/- 2.6|
|62||330 +/- 37||3.17 +/- 0.47||37.5 +/- 2.0|
|126||355 +/- 52||5.62 +/- 0.16||40.0 +/- 2.6|
Note the rate of blunting isn't linear, the loss of sharpness slows down rapidly. After 126 cuts the aggression is quite low and the knife is taking much more force to slice through the hemp and is slipping on the 1/4 inch poly quite badly. In comparion, this performance is about double that of a Twistmaster from Cold Steel with a similar edge geometry and finish [ref].
As noted in other reviews [ref], the cutting ability and edge retention on hemp was enhanced with use of a more coarse grit and more acute edge angle. Taking this idea to the extreme, this blade was ground down to a full convex profile, with use of a one inch slack belt sander. This produced a slight secondary edge bevel due to the slack in the belt with an edge profile of about 0.033" by 0.182" which is about 5.2 degrees per side.
Due to the very coarse grit finish (100 AO) and extremely acute angle, the microteeth produced were very large. There were large irregular "mini-serrations" about 0.15 mm deep, which were themselves micro-serrated with additional smaller teeth about an order of magnitude smaller. Even with this very coarse finish the blade could still shave and push cut paper. Note no polishing was done to the blade. It was simply cleaned on canvas loaded with wax paste to remove debris.
With the new edge profile and finish the hemp cutting was again repeated. Results :
|# hemp cuts||Thread||Poly||Hemp|
|0||250 +/- 37||1.35 +/- 0.27|
|2||260 +/- 32||1.15 +/- 0.21||8.0 +/- 0.7|
|6||250 +/- 5||1.10 +/- 0.13||8.5 +/- 0.7|
|14||265 +/- 29||1.25 +/- 0.03||7.5 +/- 0.7|
|30||250 +/- 8||1.35 +/- 0.05||8.5 +/- 0.7|
|62||275 +/- 2||1.60 +/- 0.24||9.5 +/- 0.7|
|126||310 +/- 13||1.50 +/- 0.13||11.5 +/- 0.7|
|254||410 +/- 42||1.60 +/- 0.05||9.5 +/- 0.7|
|510||380 +/- 37||2.20 +/- 0.05||11.0 +/- 1.3|
|1022||340 +/- 5||2.65 +/- 0.03||13.0 +/- 1.3|
|2046||410 +/- 16||2.65 +/- 0.08||20.0 +/- 1.3|
First off all it is clear that the push cutting sharpness on the thread is much lower even though the edge angle is much more acute, this is the drawback to rougher finishes. The initial performance on the poly is also lower, as the tension is also not high enough to activate the full potential of the larger micro-teeth. The full enhancement to the cutting ability is seen on the hemp slicing which shows a dramatic increase in performance. The required force is less than a third of what it was before the modifications.
The other very large immediate conclusion is that the edge retention was also hugely enhanced. The rate of blunting is also nonlinear as it was before, so the overall pattern is of the same style but the rate of change is much lower. The knife is now able to cut about 16 times more hemp before the performance has degraded to a similar level on the thread and with a similar increase in force required on the hemp, about 12 pounds.
To be a little critical, the last round of cutting was very tiring and towards the end I was getting a little sloppy, the last few cuts which took ~20 lbs was heavily influence by fatigue. Looking at the overall pattern of hemp and poly degredation it would seem sensible to conclude that the knife could have taken another round of cutting (so 4094 cuts in total), before the blunting would have been similar in extent to the previous finish and edge angle.
UPDATE : both of these were one run trials, to get more robust results they should be repeated. This isn't possible with the initial profile obviously as it was modified. It can be done with the new profile, but probably never will due to the extreme time it takes to do the cutting. Note the similar work in more recent reviews are all based on multiple trials for each run [ref].
This blade cuts very well due to the profile and holds its edge for an exceptionally long time. Of course it would not respond to prying very well, and the edge isn't suitable for metal cutting or other similar work. It can for example, see large chips from staple contacts when cutting through heavy cardboard boxes.
You can comment on this review by dropping me an email : cliffstamp[REMOVE]@cutleryscience.com. Feedback can also be seen in the in the following ARCHIVED threads on Bladeforums :
|Last updated :||Mon Jun 16 11:14:51 NDT 2003|
|Thu Jan 13 12:39:12 NST 2000|